On Feb 20, 2012, at 3:16 PM, John McCall wrote:
> On Feb 20, 2012, at 8:48 AM, Howard Hinnant wrote:
>> I'm getting the following warning on building libc++:
>>>> ../src/locale.cpp:4554:14: warning: missing field 'tm_min' initializer [-Wmissing-field-initializers]
>> tm t = {0};
>> ^
>> 1 warning generated.
>>>> I know what the warning is saying. My question is why? I presume tm_min is getting initialized to 0 as intended. The above is pretty standard fare (I thought) for zero-initializing an aggregate. Isn't this warning a little too chatty?
>> -Wmissing-field-initializers does have a special case for intentional uses of the language's default-zero-initialization rules. However, that special case is spelled {}, not {0}. If you feel that this is a really common idiom for zero-initialization, we could also add it, but I'd really prefer not to, because it neuters -Wmissing-field-initializers on an interesting class of bugs.
>> I acknowledge the argument for {0} being a more explicit "I want to zero-initialize this whole thing", but I don't actually agree. Neither {} nor {0} is being used for its obvious, literal meaning ("there is nothing to initialize here" and "there is one thing to initialize here, and I want it to be zero", respectively). Both expect the code-reader to understand the language's implicit-initialization rules. The first, however, is pretty obviously not the programmer's intended meaning when used to initialize an object that's known to carry information.
I'm content with:
#pragma clang diagnostic ignored "-Wmissing-field-initializers"
for libc++ code. Though I do suspect that this issue will come again with someone else.
Howard